Package: graphicsmagick
Version: 1.4+really1.3.38-1
Severity: wishlist
Control: found -1 1.4+really1.3.36+hg16481-2
Control: found -1 1.4+really1.3.35-1~deb10u2
[Please do not Cc: me, for I’m “on the list,” so to say, and
I try to reserve my inbox for private communication only.
I’d have set up Mail-Followup-To:, but there doesn’t seem to
be a way to make it point to the report being filed.]
It is currently possible to use $ gm convert command to show
images by writing them directly into Linux framebuffer, provided
that the /dev/fb0 device file permissions are set appropriately.
For instance, on my system, the command could be:
$ gm convert -resize 1280x1024 -gravity center -extent 1280x1024 \
-depth 8 -recolor "0 0 1 0, 0 1 0 0, 1 0 0 0, 0 0 0 1" \
IMAGEFILE\[0] rgba:/dev/fb0
Similarly, it’s possible to take screenshots, though the
only way to do so that I was able to figure out requires
a simple byte order conversion helper, like:
$ (perl -e 'use common::sense; binmode (STDIN); binmode (STDOUT);
local $/ = \(4 * 1280); while (<STDIN>) {
s/(.)(.)(.)./$3$2$1\377/g; print ($_); }' \
< /dev/fb0 \
| gm convert -size 1280x1024 -depth 8 rgba:- SCREENSHOT.png)
The obvious inconvenience here is that the framebuffer data
format (-size, -depth, but in general also the layout and
such things as the use of indexed color instead of RGB(A))
vary from system to system, depending on the hardware and
its boot- (e. g., I use video=VGA-1:1280x1024-24 on my system)
and run-time (as could be set with fbset(1), at least on
some arm64 machines) configuration.
I therefore suggest that a new ‘Linux framebuffer’ image
format is implemented in GraphicsMagick that would use the
FBIOGET_FSCREENINFO ioctl [1] to figure out the framebuffer
resolution and format before reading (writing) image data
from (to) it; like:
$ gm convert imagefile linuxfb:/dev/fb0
$ gm convert linuxfb:/dev/fb0 screenshot.png
$
[1] http://kernel.org/doc/html/latest/fb/api.html
Better still if it’d be possible to select a portion of
framebuffer for reading (without reading the whole framebuffer
first), or to put the image into a given position on screen
when writing. While this won’t turn gm(1) into a fully-featured
framebuffer image viewer, for what we have fbi(1) already,
arguably it would be rather a convenient feature to use from
scripts.
--
FSF associate member #7257 http://am-1.org/~ivan/
